1. Field of the Invention
The present invention relates to nanoemulsion comprising metabolites of ginseng saponin as an effective component and to a method for preparing the same, and to a skin-care composition for anti-aging containing the same. More particularly, the present invention relates to nanoemulsion comprising main metabolites of ginseng saponin obtained by conversion of glucose in the saponin, i.e. 20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol, called “compound K” (hereinafter, “compound K”), 20-O-β-D-glucopyranosyl-20(S)-protopanaxatriol, called “ginsenoside F1” (hereinafter, “ginsenoside F1”) and 20-O-[α-L-arabinopyranosyl(1→6)-β-D-glucopyranosyl]-20(S)-protopanaxadiol, called “compound Y” (hereinafter, “compound Y”), and admixture thereof. The present nanoemulsion may be prepared by emulsifying metabolites of ginseng saponin in fine emulsion or liposome with dermotropic emulsifier such as lecithin, by nano-emulsification such as high pressure homogenization and solvent extraction. The present nanoemulsion has enhanced skin penetration and thereby the cosmetic composition containing the same can promote proliferation of fibroblast and biosynthesis of collagen, so as to effectively prevent skin aging.
2. Description of Prior Art
Generally, skin is the first protective barrier against the surrounding environments such as change of temperature or humidity, UV and contaminants, and plays an important role in maintaining homeostasis such as thermoregulation. However, the skin may be damaged by excessive physical or chemical irritations, stress or sub-alimentation, resulting in losing normal functions and elasticity or so, to cause keratinization and to form wrinkles. On this, in order to prevent skin aging and to maintain healthy and elastic skin, a lot of efforts have been made to develop cosmetics containing biologically active materials obtained from animals, plants or microorganisms that play a role in maintaining skin functions and in activating skin cells, resulting in effectively controlling skin aging.
However, these active materials have some drawbacks such as insufficient efficacy or side effects such as skin irritation.
Accordingly, much researches has been made in order to provide cosmetic materials for anti-aging without skin irritation. Specially, many concerns on the extracts of ginseng led to extensive studies. These studies have widely focused on ginseng extracts, i.e. ginseng saponins and the intestinal flora metabolites thereof, which are obtained by isolation and conversion of glucose (via acid or alkaline hydrolysis or enzyme reaction), for example, compound K, ginsenoside F1 and compound Y.
Ginseng saponin has a specific chemical structure in which sugar such as glucose, rhamnose, xylose or arabinose is linked via ether bond to R1, R2 or R3 positioned-alcoholic OH of aglycon of triterpene, a family of dammarane. Up to date, in total 29 kinds of saponins have been identified. Shibata, in 1964, called each component of said ginseng saponin “ginsenoside”, which refers to glycoside contained in ginseng. Ginsenosides are classified into ginsenoside-Ro which is a family of oleanane saponin, and ginsenoside-Ra, -Rb1, -Rb2, -Rc, -Rd, -Re, -Rf, -Rg1, -Rg2, -Rg3 and -Rh according to the developing orders on TLC (thin-layer chromatography).
These ginseng saponins were found to be completely different from those found in about 750 other kinds of herbs in viewpoint of chemical structure and medical activity. Especially, ginseng saponins were revealed to have mild medicinal property and no toxicity or little hemolysis with excessive administration.
Further, it was reported that ginseng saponin applied on the skin in the form of liposome, which is a complex with phospholipid, has effects on imparting vitality to aged skin, increasing elasticity and hydration of the skin and accelerating blood circulation of the skin. (Curri. S B, Gezz, Z, Longhi, M G, Castelpietra, R: Fitoterapia, 57, 217(1986); Gezzi, A, Longhi, M G, Mazzoleni, R, Curri, S B: Fitoterapia, 57, 15(1986); Bombardelli, E. Curri, S B, Gariboldi, P L: Proc. 5th Intl. Ginseng Sym. Seoul Korea, 11(1988))
Thereafter, in order to apply ginseng saponin as an anti-aging material, ginseng aglycon was bioconverted for enhancing skin penetration and tested for the efficacy on the skin, which was confirmed as the same as that of ginseng saponin.
As for the applications of ginseng extracts or saponins, U.S. Pat. Nos. 5,565,207, 5,567,419, 5,578,312, 5,663,160, 5,626,868, 5,753,242, 5,747,300, 5,853,705, 6,027,728, 6,063,366, 6,221,372 and 6,228,378 disclosed cosmetic compositions and U.S. Pat. Nos. 5,569,459, 5,571,516, 5,587,167, 5,674,488, 5,665,393, 5,629,316, 5,776,460, 5,739,165, 5,916,555, 6,071,521, 6,083,512 and 6,255,313 disclosed pharmaceutical compositions. In addition, U.S. Pat. Nos. 5,591,611, 5,591,612, 5,736,380, 5,789,392, 5,780,620, 5,922,580, 5,935,636, 6,132,726, 6,156,817 and 6,207,164 disclosed methods for isolation and purification of ginseng saponins.
However, ginseng saponin is extremely hydrophilic and has high molecular weight due to its chemical structure in which sugar is linked via ether bond to R1, R2 or R3 positioned-alcoholic OH of dammarane aglycon, thereby interfering with penetration into stratum corneum and absorption into inner dermis.
While, extensive studies on saponin metabolites revealed that the efficacy of ginseng saponin is due to the metabolites decomposed by human intestinal bacteria, not due to saponin itself. For example, ginsenoside-Rh1, Rh2 and F1, compound K and others with one glucose linked to aglycon of saponin have been reported to have pharmacological effects such as inhibitions of proliferations of cancerous cells and tumors, and enlargement of activities of anticancer agents.
Nevertheless, methods for application onto the skin and formulation of the compound K, ginsenoside F1 and compound Y obtained by removing a part of sugar moiety from ginseng saponin have not been researched yet.
Under these circumstances, in order to find a method for application of the compound K, ginsenoside F1 and compound Y onto the skin, the present inventors have conducted extensive studies on micro- and nano-emulsification. As a result thereof, the inventors found that nanoemulsion, obtained by emulsifying metabolites of ginseng saponin in fine emulsion or liposome with dermotropic emulsifier by nano-emulsification, has enhanced skin penetration and thereby can be applied to skin-care compositions for anti-aging. The present cosmetic composition containing the nanoemulsion can promote proliferation of fibroblast and biosynthesis of collagen, so to effectively prevent skin aging.